Method of transforming a pre-determined force or pressure pattern

ABSTRACT

The present invention is related to a method of transforming a pre-determined force or pressure pattern on a lid element through said lid element onto a second element having a planar or non-planar surface. According to a first method step an optimized preformation-shape of said lid element and/or said second element is calculated dependent on the operating parameters of said second element. At least one of said elements is preformed according to said optimized preformation-shape using a primary shaping or reshaping technique. Said lid element is connected to said second element after application of an external force at at least one predetermined force application point by mechanical fastening or generating an adhesive bond between said elements.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on U.S. Provisional Application No. 60/645,613 filed Jan. 24, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved method of and device for tightly and uniformly sealing any type of fluidic structure, in particular to components made from flat, solid, yet flexible, semi-finished parts such as planar lab-on-a-chip structures.

2. Description of the Prior Art

US 2002/0155337 A1 discloses to convex fuel manifold providing uniform pressure seal to a fuel cell stack. According to this disclosure a reactant gas manifold for a fuel cell stack assembly having a generally planar configuration with two opposing long sides joined together by two opposing short ends, the sides and ends having substantially small surfaces for sealing against a fuel cell stack. The surfaces are manufactured convex. This results when the manifold distorts as a consequence of said short ends being bonded to a fuel cell stack, the sealing surfaces of the long sides will provide substantially uniform sealing pressure throughout the length thereof.

U.S. Pat. No. 6,451,264 B1 is related to a fluid flow control in curved capillary channels. According to this solution a capillary pathway is dimensioned so that the driving force for the movement of liquid through the capillary pathway arises from capillary pressure. A plurality of groups of microstructures affixed in the capillary pathway within discrete segments of the pathway for facilitating the transport of a liquid around curved portions of said pathway. Capillary channels can be coupled between adjacent groups of microstructures to either the inner and outer wall of the capillary pathway. The width of each capillary channel is generally smaller than the capillary pathway to which it is connected can be varied to achieve differences in full initiation. The grouped microstructures are spaced from each other within each group on a nearest neighbour basis by less than that necessary to achieve capillary flow of liquid within each group. Each group of microstructures are spaced from any adjacent group by an inter-group space greater than the width of any adjacent capillary channels connected to the capillary pathway. Generally, the microstructures are centered on centers which are equally spaced from each other and microstructures that are located closer to the inner wall of any curve in the capillary pathway are generally smaller than those microstructures located closer to the outer wall. This combination of structural features causes fluids to flow through the capillary pathway so that the rate of flow is somewhat non-uniform as compared to the fluid traveling around curved portions of the capillary pathway. The meniscus appearing to pass momentarily at each inter-group space, the flow being somewhat smaller near the inner wall of a curved portion as compared to the outer wall.

In almost every case of a micro fluidic device, a more or less complicated channel network structure, located on the surface of a solid, needs to be shut off from the outside world, using a lid or any sort of a top cover, in order to prevent liquid from the inside flowing out at places other than desired to protect users from possible dangerous fluids leaking from the channel network and to prevent the inside from being contaminated with particles, etc..

Up to date, several different techniques are being used to fulfill the task described above. One way of covering a flat fluidic structure is to use a suitable glue. The glue can be applied using glue dispensers, roll-on techniques, printing techniques or sprays. Care has to be taken that no glue contaminates the often delicate structures within the fluidic network, clogging them or gluing movable parts against each other or to a sort of a carrier chip. Since micro fluidics usually deal with very small channel geometries (often 100 micrometers and way below), application of an exact amount of glue to the exactly right place is often hard to achieve and needs significant expertise of manual workers and/or high precision machines with the ability of ensuring the high quality demands applying to life sciences and health care products. This, however, usually results in high costs for the fabrication of the base-lid connection. Furthermore, contamination of substances used for detection of certain ingredients contained in the fluids flowing through the channels has to be avoided. Since most glues use solvents that more or less rapidly evaporate into the air as well as emigrate into the surrounding material that they have been applied onto, it must be assured sure that these solvents do not interfere with the detection taking place within the channels (such as fluorescence detection, for example). More important, it must be assured that no remnants of any type come in contact with the liquids in the case of re-entering the human body (pharmaceutical application fluidics come up to give an example).

Furthermore, said solvents often remain at least in small quantities within the closed structures for a rather long time, for months or even years. They are therefore not favourable for being used in the above-mentioned fields of application.

Another often-used way of quickly and securely gluing parts together is by using ultraviolet-curable adhesives. Since they remain viscous until exposed to ultraviolet light, the parts can be readjusted and even partly cleaned from excess glue before fixing. The fixation process itself usually takes only a couple of seconds. Adversely, UV radiation sometimes might affect detection substances, such as dyes, located inside the micro fluidic system. Also, not all polymers are transparent to UV light, especially when coloured.

A second way for fulfilling the task in question is thermal bonding, using the capability of globally heating up the bodies to be connected, while melting only the material that forms the contact surfaces. This technique is useful especially when polymeric materials are being used. Melting can be induced by placing an intermediate material sheet between the contact areas that has a melting point significantly below the one of the base and lid material, followed by heating up the complete structure above the softening/melting point of the connection layer, while applying some pressure. Many polymers are available in grades with different melting points, whereas the basic material is kept the same. For example, TOPAS®, a cycloolefin-copolymer from TICONA, is available with glass transition temperatures of 68, 80, 136, 140, 160 and 180° C., respectively. However, the molecular structures of the underlying basic material and the melting layer remain identical. This results in a homogenous material cross section, since no significantly other material has to be used.

On the other hand, the same problems known from using viscous gluing fluids discussed above apply here as well: softened material can flow into the channel structures, movement of parts can be obstructed. Furthermore, many biomedical applications are sensitive to high temperatures within the channels since they comprise temperature damageable substances that are often destroyed by temperatures higher than 40° C.-60° C. Since the whole structure is heated up (e.g., by placing it in an oven), thermal bonding is often inappropriate for connecting parts used in biomedical applications. Last but not least, heating up and cooling down is a time-consuming process, making it not first choice for mass produced parts where short cycle times are essential.

Another way to induce melting is to use laser irradiation that can be very precisely directed to the places where the surfaces should be connected to each other, resulting in locally melting the material only inside the connection surfaces. This not only minimizes the amount of energy (by adjusting the laser power), but also enables a very exact location of the welding seam since lasers can have less than 100 micrometers small focal spots that can be directed very accurately along pre-described paths. By using fast laser scanners or masks, even larger areas can easily and quickly be heated up. It has to be emphasized that heating takes place only at the contact area and not in the depth of the material, depending on the absorption coefficient that indicates the ability of the material to absorb irradiation of a certain wavelength. It also has to be understood that one of the contact partners must be transparent to said wavelength whereas the other has to absorb light of the same wavelength quite well. This, of course, does limit the area of application for said technology since not all materials are available in transparent and non-transparent types nor can they be made to be so. Since diagnostic micro fluidic devices often use some sort of light detection on the embedded sample, the need for one absorbing contact partner might inhibit proper functioning of the device so that usage of laser-induced heating (“laser welding”) as a connection technique cannot be used. Also, the usually high initial costs for laser welding systems might keep otherwise potential users from employing this technique.

Where applicable, however, laser welding is a very fast and reliable method to fasten and tightly seal any type of fluidic device (as long as melting material is present at least at the contact surface). Since no additional material for the connection layer is necessary, no further steps than making sure that the proper absorption/transmission is possible have to be taken.

A third and quite simple way of sealing fluidic structures is to mechanically press lid and base against each other. Depending on the pressure inside the channels, the surface quality of the contact surfaces and the available external pressure, it may or may not be necessary to take actions to improve sealing by placing additional sealing layers in between the contact surfaces. Usually, those are soft, rubber-like materials.

Advantageous is the fact that mechanical clamping is usually cheap, fast and secure, if properly adjusted to fulfil all requirements of the task. On the other hand, the external pressing forces have to be applied somehow. This might be achieved using additional screws, clips or even frames that hold and press the contact partners against one another. All these solutions require space and possibly other materials than the one of the fluidic system, in turn resulting in higher end prices and possibly bulkier devices. But still, mechanical fastening has the advantages over other joining methods due to its speed and simplicity. A main disadvantage of entirely flat shaped contact surfaces is the fact that distributions of contact pressures are highly dependent on the places where the external compression forces are coupled into the contact partners from the outside. For example, if a flat, square-shaped device is held together by screws located in its four corners, the contact pressure will be very high close to the corners, and will significantly lesson towards the centers of the surfaces. Uneven pressure distribution can even go so far that a gap is formed in the center, since the lid might be strongly deformed through excessive compression forces in way that they lead to unwanted outward bulging of the lid (and/or the base).

Uneven pressure distribution, however, usually leads to leakage of the fluidic system, if not even the lowest contact pressure is high enough to seal the system (i.e. higher than the highest fluidic pressure plus a safety factor). In order to ensure proper sealing, the compression forces need to be rather high and the lateral dimensions of the devices may not, in comparison to its thickness, exceed a certain value (approx. 5:1 to 10:1). Otherwise, bulging may occur. Such practice is not considered to be efficient since high compression forces result in higher loads on places where otherwise being unnecessary, in enhanced creep (if using polymeric materials), the need for stiffer constructions, and the like.

SUMMARY OF THE INVENTION

The present invention discloses a significant improvement regarding the problem of uniformly sealing a fluidic device with a protective lid or cover, respectively. Starting from the fact the pure mechanical sealing could be suitable for many applications if the contact pressure between base and lid would be more uniform, a way of overcoming this disadvantage is presented hereinafter.

Basically, the invention proposes to change the shape of at least one or both joined components or partners, preferably the lid, in a way that when pressed against its counterpart, uniform contact pressure occurs. This is achieved by exactly calculating a curvature of the contact partner(s) resulting in said uniform or an intentionally non-uniform pressure distribution. It has to be understood that the shape calculated is valid only for this special case of geometry, thickness, material stiffness, desired pressure-tightness and clamping forces.

Nevertheless, the basic principle can be used for virtually all shapes, materials, etc., although the resulting shapes can look rather different if compared with one another. This is the reason why only some preferred embodiments of the invention can be described hereinafter more in detail.

The above-mentioned external forces either can be coupled into a lid/fluidic structure either by application of the external forces along the outward edges, the corners or other points of the lid-shaped element's outer surface or alternatively can be created after application of said lid-shaped element on the sealing surface of the fluidic structure or by creation of connecting points by means of laser welding or the like. In the latter case the connecting points are established by the laser welding points themselves between the lower surface of the lid-shaped element and the sealing surface of the fluidic structure to be sealed. In the case the preformed lid element is subject to external forces applied thereon, after flattening of the preformed lid element and performing of the laser welding operation, said external forces are removed.

The present invention can be used for sealing of fluidic structures such as micro or macro fluidic structures, which either process a liquid or which on the other hand may process a gaseous medium, or a combination thereof. Dependent on the coupling-in of external clamping forces either by means of mechanical structures or by means of thermal (laser welding) or adhesive (gluing) bonding, a uniform or an intentionally non-uniform pressure distribution between a lid-shaped element and a fluidic structure such as a micro fluidic system or a macro fluidic system can be achieved. The external forces either applied by means of mechanical fasteners or by creation of a welding point between a lid-shaped element and a fluidic structure establish the sealing function between the lower surface of the pre-formed lid-shaped element and the respective sealing surface of the fluidic structure allocated at the top thereof. It is to be noted, that upon laser welding, i.e. sealing, the lid-shaped element and the fluidic structure external forces are required to allocate the pre-formed lid-shaped element for responding to the for example planar sealing surface of the fluidic structure to be sealed. Depending on the respective shape of the fluidic structure, the pre-formed lid-shaped element can either be of a regular (circular, square, rectangular) or irregular (pre-form contoured) shape. Depending on the distribution of the external pressure forces, to be coupled in at determined force application points, lines or areas or a combination thereof the respective contacting partners, i.e. the lid-shaped element, and the sealing surface of the fluidic device to be sealed can either be planar or be uneven. The outer geometry of said lid-shaped element can either be symmetric, such as circular or rectangular or can adopt any other shape. The pressure distribution achievable between the bottom of said lid-shaped element and the sealing surface of the fluidic device can be chosen to be uniform or can be chosen to be intentionally non-uniform. The external pressure can be coupled in for example at the four corners of a square or a rectangular shaped system of lid-shaped element and fluidic structure. The external forces can likewise be coupled in along lines or areas or a combination of areas and lines and points with respect to the geometry of the lid-shaped element and the fluidic structure to be sealed.

Although the following examples show a combination of only two partners, with one being flat, the other being pre-formed, the scope of the invention covers the case of two (usually contrarily) pre-formed contact partners as well. It also covers a combination of more than two contact partners; also three or more structures can be optimized in a way that when pressed together as a stack, equal or intentionally unequal contact pressure distributions occur.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is more fully described herein below, with reference to the drawings, in which:

FIG. 1 a schematically illustrates a contact pressure distribution on one of two flat, rectangular contact partners when external pressing forces are coupled in at two corners,

FIG. 1 b shows the same geometry as shown in FIG. 1 a, but when forces are coupled in along all borders,

FIG. 2 shows the resulting contact distribution, when shape is optimized by a computer simulation software,

FIG. 3 shows a schematic example of a lid for a rectangular contact surface that has been optimized for even pressure distribution,

FIG. 4 shows a cross sectional view of an exemplary clamp-fastening mechanism, i.e. a mechanical fastening,

FIG. 5 shows a perspective view of a circular-shaped lid with underlying base structure,

FIG. 6 shows a cross-section through a circular the structure of FIG. 5,

FIG. 7 shows a square-shaped lid shown with an underlying base structure, such as a fluidic structure

FIG. 8 shows a cross-sectional view, in perspective, of the square-shaped lid and base structure according to FIG. 7,

FIG. 9 shows a cross-sectional view, in elevation, of the square-shaped lid from FIG. 7 arranged above a fluidic device,

FIG. 10 shows the rectangular-shaped lid in full view covering a fluidic structure,

FIG. 11 shows a perspective cross-sectional view of a rectangular-shaped lid covering a fluidic structure,

FIG. 12 shows a long-side cross-sectional elevation view of a pre-formed-lid and base from FIG. 11,

FIG. 13 shows a long-side-elevation-view of the pre-formed lid from FIG. 10,

FIG. 14 shows a perspective cross-sectional short-side-view of a fluidic device being covered by a rectangular-shaped lid from FIG. 10, and

FIG. 15 shows a cross-sectional short-side-top-view of the pre-formed rectangular lid covering a fluidic structure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention addresses the problem of uniform or intentionally non-uniform contact pressure distribution when pressing, for example two flat surfaces against each other, using external clamping forces that are not distributed evenly over the outer surface of said contact partners.

To illustrate the invention, the embodiments of two square, two rectangular and two circular contact partners are described. In case of square or rectangular lids 70, 80 the external forces may be coupled in at four corners 16, 18, 20, 22 of the contacting partners. In case of a circular lid 50 the external forces may be coupled in at at least one force application point along the circumference of said circular shaped lid element 50.

For different coupling settings, e.g. with forces coupling in along the outer edges or a combination of point and line loads the results will look more or less different from depicted basic examples given here in greater detail. Even asymmetric pre-deformations are possible but shall not be introduced here as simple examples.

“Coupling in” in this context does not limit the procedure of pressing the bodies together using any special part for connection, but rather describes the bare fact that base, i.e. a fluidic device 38 and lid 50, 70, 80 are pressed against each other due to external forces. If no other efforts are undertaken, the pressure distribution of the contact area between the partners look like that depicted in FIG. 1 a and 1 b, respectively, depending on the place(s), where the parts are pressed together. The contact pressures are highest in the corners 16, 18, 20, 22 of borders, respectively, diminishing towards the center of the flat structure 12 that represents the base that carries a fluidic system not given in greater detail here. As a result, only a fluidic pressure that is substantially lower than the lowest contact pressure emanating from the external forces can be sealed, even if additional soft sealing intermediate layers are used.

As input parameters a software algorithm uses the desired lid shape, which is usually a flat structure similar to structure 12 but with a thickness that is usually less than or equal to the thickness of the base structure 12, the external force-coupling points (e.g. the four corners 16, 18, 20, 22) and desired contact pressure (at least a bit larger than the fluidic pressure within the system). It then calculates a new shape for the body in question such as the lid 50, 70, 80, which in turn leads, when pressed down at the previously described external force-coupling points, e.g. the corners 16, 18, 20, 22 against the other contact partner (a fluidic device 12/38) to a uniform distribution of contact pressure over the entire contact surface, i.e. said sealing surface 32.

In FIG. 2 the resulting contact distribution calculated by contact simulation software after optimization of the lid-shape is given just before the corners 16, 18, 20, 22, respectively, touch the corners of a base structure. As can be derived from FIG. 2, the contact pressures are distributed much more evenly over the entire surface, no pressure concentration is visible at the corners 16, 18, 20, 22 as compared to FIG. 1. The flat structure given in FIG. 2 has an optimized pressure distribution which is characterized by a very low pressure in the vicinity of said four corner points 16, 18, 20 and 22, respectively. The pressure increases according to the illustration of the 90°-segments given in a pointed illustration, representing a very low pressure, the thin dashed lines representing a higher pressure distribution along the 90°-segment and by the 90°-segment given in dashed lines in a stronger thickness. In contrast to the optimized shape given in FIG. 2 in the embodiment according to FIG. 1 b) a very high pressure is present in the vicinity of said four corners 16, 18, 20 and 22, respectively, which however decreases towards the center of said flat structure 12 given in FIG. 1 b.

FIG. 3 shows the exemplary cross-section of a lid 30 that is to be pressed against a fluidic device 38 using external forces. For the case in question, the shape may be described as generally saddle-shaped. The center is lower than the short side; all corners (16, 18, 20, 22) are higher than the centers of the sides, and the long sides' centers are even below the center of the whole surface.

As a result of using such a shape, far less external forces are necessary to generate sufficient high contact and sealing pressures inside the fluidic system 38 in turn leading to lower stresses within the bodies, a better material utilization and less constructional efforts to provide the external forces necessary.

In contrast, only by using a number of iterating optimization steps, calculated by special computer software, a sufficient solution for the described problem may be found. Nevertheless, if by advances in mathematics, a more simple, analytical solution to the task should be available, the basic principle of using specially curved bodies to obtain predetermined contact pressure distributions is not affected.

In the following description, some of the common shapes that are used for fluidic systems are discussed in greater detail, exemplary solutions for optimized shapes are presented. For the simple case of a square surface with corner bearing, the resulting shape looks like that depicted in the embodiments given in FIGS. 7, 8 and 9, respectively. Since all loads are symmetrical, the resulting shape is symmetrical, too. Before joining, the corners are bent upwards and the center of the contact surface constitutes the lowest point. If the external forces are not only coupled in at the corners, but along the length of the four sides, the shape (not depicted) will slightly change.

If one of the sides of the contact surface is longer than the other, the shape of the optimized geometry changes to the one described above as depicted in FIG. 10, 11 and 15, respectively.

For the basic case of a circular contact shape, FIG. 5 and FIG. 6 constitute the optimized shape.

The present invention is not limited to adaptation of only one of the contact partners. It is also conceivable that both partners, the lid as well as the base, can be optimized to fulfill the task of evenly or intentional unevenly distribute contact pressures. The main advantage resides in the fact that each of the contact partners needs less deformation than in the case of a single contact partner being pre-deformed. This enables the invention to cover even a broader range of pressures within fluidic systems.

Besides the shapes described in detail, the technique presented is usable for all other two-dimensional shapes as well. Commonly used shapes include such shapes with the corners being rounded, the corners having an elliptical shape as well as triangular or even asymmetrical shapes.

A change in the boundary condition from uniform to intentionally non-uniform contact pressure distribution (such as more pressure on one half, less on the other half, or more at the center, less at the borders) can be taken into account by the optimization software that produces a shape that leads to the desired contact pressure distribution. Of course, limits that are given by maximal strain/stress within the material have to be taken into account. Nevertheless, by designing the distribution of contact pressures in an optimized way that follows the particular task, the overall performance of the effectiveness of closing and sealing can be further optimized, material saved and costs significantly reduced.

Up to this point, only a vague description of how the external pressures/forces that hold the two contact partners together are coupled in has been given. Therefore, some of the preferred techniques how lid and base can be pressed together are discussed herein below in more detail.

One simple and very common way of holding together two separate bodies is to use fastening elements such as screws or bolts. By providing two adjacent holes at the corners of both partners and the usage of nuts and bolts or by having a threaded hole and a matching screw or bolt, the partners can securely and reversibly be held together. A disadvantage is the additional space that such a mechanism uses and the fact that additional material is necessary.

This disadvantage is partly reduced by using rivets that are brought into the holes. This method is fast, accurate enough, and rivets can be made from plastics as well as from metals. Since the spring force of the concave-shaped lid acts against the clamping force of the rivet, there is always a remaining contact pressure between the two contact partners even if the rivets are losing their clamping force gradually over time (creeping effect for the case of plastic material being used). Of course, it must be ensured that the remaining contact pressure is sufficient for the sealing task.

Another method gaining more and more importance, especially in the application of life sciences and health care, is the usage of laser welding techniques. Basically, a laser beam heats up a defined region of the contact area, preferably at the corners or outer boundaries that are not used for fluidics. Recently, lasers with very small focus spots have been made available that allow for welds as close as a few micrometers to delicate channel structures without changing their shape irreversibly by melting their respective sidewalls. Laser welding can be very fast and accurate and has only the disadvantage of higher initial costs for the laser welding machine, irreversibility of the connection and heat being temporarily coupled into the surfaces that are to be connected. Advantageous is especially the fact that the seams are hermetically sealed, since a rigid bond between both contact surfaces is developed, that often reaches material stiffness close to the original material. Seams are transparent and can be very thin so that minimal additional area is needed. In fact, almost all the area surrounding the fluid channels can be used for the laser welding of the contact surfaces.

Another method of providing force to press both contact partners against each other is to use mechanical clamp-fasteners as illustrated in FIG. 4. A fastener 46 can either be part of the lid 30, 50, 70, 80 or the base 38, i.e. the fluidic structure, covering the opposite partner when brought into close contact so that both are held in place by a form fit between a chip and a corresponding fastening mechanism. Such mechanical fasteners 46 are widely used in the plastic industry, where fast and easy connection of a multitude of single parts must be realized with minimal effort and no additional materials such as glue or screws. In connection with fluidic systems 38 the lack of screws leaves more space for the fluidic system itself, i.e. for the geometry, the length of the channels and therefore leaves more freedom of choice in view of direction and shaping of channels. Since the spring force of the curved lid (or the curved base) always puts a positive pressure against the contact surfaces, sealing is ensured as long as the remaining pressure is higher than the fluidic pressure inside the system. By use of additional intermediate sealing layers, leakage problems can further be reduced or even be entirely eliminated.

According to the illustration given in FIG. 4, a fluidic device 38 is surrounded by a hook-shaped fastening element 46 which provides for a tight form fit with a pre-formed lid structure 30. The pre-formed lid structure 30 sealingly covers a top side 42 of said fluidic device 38, which is in turn subject of an externally applied pressure gradient, which in turn is imposed on the liquid which is to be separated within said fluidic device 38. Said hook-shaped fastening element 46 surrounds a length or a width portion of said fluidic device 38 and clamps said pre-formed lid 30 onto said fluidic structure 38, only schematically given in FIG. 4. Said mechanical fastening element 46 given schematically in the illustration according to FIG. 4 either can be replaced by a bolt, by a screw/nut system or by a spring-load design allowing for a tight sealing fit between said pre-formed lid structure 30 and a sealing surface 32 on said top side 42 of the fluidic device 38. Although only one mechanical fastening element 46 is given in the illustration according to FIG. 4 a plurality of said mechanical fastening elements 46 are to be arranged on said pre-formed lid structure 30. In case the pre-formed lid 30 is an injection-molded plastic component, said mechanical fastening elements 46 can be directly formed upon injection-molding of said pre-formed lid structure 30 arranged thereon without requiring an additional molding step.

An additional way allowing the use of only one fastening element 46 is to replace its adjacent fastening element by a hinge that either can be subsequently to lid-and base-fabrication being put in place or that can be injection molded as an elastic joint, connecting base and lid-permanently. Such a hinge would have to be so short that it provides no gap between base and lid when the adjacent single fastening mechanism has been closed. As can be derived from the illustration given in FIG. 4 that mechanical fastening element 46 in its mounted stage contacts a bottom side 44 of the fluidic structure 38. On the other hand the bottom of the pre-formed lid structure 30 contacts the top side 42 of the fluidic structure 38 having a gradually opened gap extending towards the hook-shaped fastening element 46 according to the illustration given in FIG. 4. The gap is shown for illustration purposes only.

In the embodiment according to FIG. 5 an entire circular-shaped lid 50 is illustrated. Schematically a sealing surface 32 of a fluidic device 38 is given. From said reference line 66 extending through the entire diameter of said circular-shaped lid 50, a preformation depth 60 extends to the lowermost point of the top side 52 of said circular-shaped lid 50. An external load in case of circular-shaped lid 50 is to be applied around the entire rim 62 limiting the top side 52 of said circular lid 50. The pressure application points 36 as shown in connection with FIG. 3 would be applied in adjacent positions around the entire circumference of said rim 62 and not only on corners 16, 18, 20, 22, as in the embodiment according to FIG. 3 in which said flat structure 12 is a rectangular structure. By applying an external force onto the rim 62 of said circular-shaped lid 50 in the mounted state on a fluidic device 38, not shown in greater detail in FIG. 6, a uniform contact pressure is obtained between the bottom side 54 of said circular lid 50 and the sealing surface 32 when the lid element is pressed down to the base. According to the degree of preformation of said circular lid 50 in the mounted stage on a sealing surface 32, a uniform pressure distribution is obtained. Vice versa, the counterpart, i.e. in this case the sealing surface 32, could be manufactured with a curvature, whereas the circular-shaped lid 50 in this case would be manufactured as a substantially planar structure. Thus, the even pressure distribution and the sealing effect would be imposed by the respective other part of the system lid/fluidic device.

FIGS. 5 and 6 further show that with respect to the sealing surface 32 of a fluidic device, a preformation curvature is provided between said sealing surface 32 and the bottom side 54 of said circular-shaped lid 50. The curvature depends on the optimized shape according to which said circular-shaped lid 50 is manufactured.

FIG. 6 shows a cross-section through the circular-shaped lid according to the present invention. Said circular lid 50 is manufactured in a thickness which is labeled by reference numeral 56. The curvature of said circular lid 50 depends on the external pressure gradient to which said fluidic device 38 is subjected. Further, the curvature of said circular-shaped lid 50 depends on the thickness 56 of the circular lid. In the embodiment given in FIG. 6 said circular lid 50 comprises a top surface 52 which is shaped concave whereas a bottom surface 54 of said circular lid 50 is shaped in a convex fashion. Reference numeral 66 depicts a reference line from which for instance a preformation-depth 60 can be measured. The reference line 66 is drawn through the equatorial-plane of said circular lid 50. In the center of said top side 52, a maximum preformation depth 60 is obtained as compared to the outer peripheral areas of said substantially concave-shaped top side 52 of said circular lid 50.

The circular lid 50 given in FIG. 6 in a cross-sectional view, preferably is manufactured by an injection molding process whereby said preformation, i.e. its respective top side 52 and its respective bottom side 54, are obtained.

FIG. 7 shows a schematically given fluidic device being covered by a square-shaped lid 70 having a thickness as indicated by reference numeral 72. The lid has a top surface 52 and a bottom surface 54 as already mentioned in connection with the embodiment given in FIG. 5 and 6, i.e. said circular-shaped lid 50. In the embodiment given in FIG. 7, a length of said square-shaped lid 70 is identified by reference numeral 24, whereas a width of said square-shaped lid 70 is identified by reference numeral 26, respectively. In this case the length 24 is identical to the width 26. The pre-formed square-shaped lid 70 according to the embodiment given in FIG. 7 comprises four corners 16, 18, 20 and 22, respectively. Said square-shaped lid 70 according to FIG. 7 is pre-formed in three dimensions. Along the length 24 of said square-shaped lid 70 the reference line 66 is shown. With respect to said reference line 66 said top side 52 of said lid 70 has a second preformation depth 78. The maximum thereof is indicated by reference numeral 78 which is positioned in the middle of said length 24. On the other hand, said square-shaped lid 70 is pre-formed along its width 26 with respect to reference line 66. The width 26 between said first corner 16 and said fourth corner 22 is formed concave, the opposite width 26 of square-shaped lid 70 is formed in a concave manner with respect to reference line 66 drawn between the second corner 18 and the third corner 20, respectively. A first preformation depth 76 along said width 26 may be equal to said second preformation depth 78 along the length or may vary according to the respective optimized curvature. Thus, depending on the thickness 72 of said square-shaped lid 70 upon mounting of said square-shaped lid 70 on the sealing surface 32 of the fluidic device 38 an even pressure distribution and in consequence thereof an even sealing effect is obtained according to the present invention.

Given the shape of the square-shaped lid 70 in the embodiment of FIG. 7 the respective second corner 18 and the third corner 20 do not yet contact said sealing surface 32 in the stage shown in FIG. 7. Upon application of external forces to the first corner 16 and said fourth corner 22, a contact of the respective sealing surface 32 upon mechanically fastening said square-shaped lid 70 on said fluidic device 38 for example by fastening elements as given in FIG. 4, is established. Alternatively, said sealing zone between the bottom side 54 and the sealing surface 32 can be obtained by laser welding the surfaces at the outer corners of said contact partners 38, 70 together. By laser welding a melting process is induced between the contacting partners 38 and 70, respectively, which can be very precisely directed to the places where the surfaces 32, 54 should be bonded to each other, i.e. at their corners or along the their outer borders. Laser welding results in a locally melting of material on the inside only of the surfaces 32, 54 to be connected. This not only minimizes the amount of energy (by adjusting the laser power), but also provides for a very exact location of the welding seam, since lasers can have less than 100 micrometers small focal spots which can be directed very accurately along pre-described paths. In the embodiment of FIG. 7 said pre-described path would only be at the four corners, in another case where optimized lid shape is not depicted here the length 24 and the width 26 of said square-shaped lid 70 could define the welding paths. By using fast laser scanners or masks even larger areas can easily and quite fast be heated up. Heating takes place only at the contact area and not within the depth of the materials of said square-shaped lid 70 or said fluidic device 38. The penetration depends on the absorption coefficient that indicates the ability of the material to absorb irradiation of a certain wavelength. It also has to be understood that one of the contact partners 30, 70 must be transparent to said respective wavelength, whereas the other has to absorb light of the same wavelength to an extent to produce the necessary heat. Where applicable, laser welding is a very fast and reliable method to fasten and tightly seal any lid/fluidic device-system as long as melting material is present at least at the contact surface, such as the sealing surface 32 of the fluidic device 38. Since no additional material for the connection layer is necessary, no further steps than making sure that proper absorption/transmission is possible have to be taken. The fact that no additional material for the generation of the connection between said square-shaped lid 70 at the bottom side 54 thereof with said sealing surface 32 of the fluidic device 38 is necessary, has the advantageous effect, that no contamination of the inner structures of said fluidic device 38 occurs, due to the fact that no additional material is necessary. The same holds true for mechanically fastening devices as given for example schematically in FIG. 4 or using bolts or nut/screw systems for fastening said square-shaped lid 70 on the sealing surface 32 of said fluidic device 38.

By connecting a pre-formed square-shaped lid 70 as given in FIG. 7 to the substantially planar sealing surface 32 of said fluidic device 38 an even pressure distribution is obtained for the entire surface, i.e. the sealing zone between the bottom surface 54 and the sealing surface 32.

FIG. 8 depicts the said square-shaped lid according to FIG. 7 in a perspective cross-sectional view. Parallel to said length 24 of said pre-formed square-shaped lid 70 a reference line 66 is drawn. With respect to the reference line 66 between the first corner 16 and the second corner 18, respectively, the concave edge 74 extends along the direction of width 26. Reference numeral 26 in FIG. 8 depicts only one half of said width. Said curvature 74 adopts a maximum second preformation depth 78 in the middle of said length 24 between the first corner 16 and the second corner 18, respectively. With respect to the reference line 66 the second preformation depth 78 shows the preformation of said concave curvature 74 the maximum of which is located in the middle of said length 24 between said first corner 16 and said second corner 18, respectively.

With respect to the sealing surface 32 of a fluidic device not shown in greater detail in FIG. 8, said corners 16, 18 and the edges of said pre-formed square-shaped lid 70, respectively do not contact said sealing surface 32. Upon application of an external clamping force at the force application points 36 shown which are identical to the positions of the first corner 16 and second corner 18, said pre-formed square-shaped lid 70 will adopt a substantially planar configuration. As a result said sealing surface 32 is covered by the bottom side 54 of the pre-formed square-shaped lid 70. By clamping said pre-formed square-shaped lid 70 onto said sealing surface 32 an even pressure distribution is obtained, allowing for sealing of a fluidic device 38 as schematically given in FIG. 7 the liquid processed therein being subjected to an external pressure gradient.

Instead of mechanically fastening said pre-formed square-shaped lid 70 onto said fluidic device 38 by means of clamping elements 46 as given schematically in FIG. 4 it is conceivable to laser-weld or glue the contacting area along the length 24 and the width 26 of the pre-formed square-shaped lid 70 with the upper area of said fluidic device 38.

FIG. 9 shows an elevation view of the cross-section of the square-shaped lid arranged above a fluidic device of FIGS. 7 and 8, with the square-shaped lid 70 shown in its pre-formed, i.e. not-mounted stage on the fluidic device 38. Said square-shaped lid 70 comprises four corners 16, 18, 20 and 22, respectively, of which the first corner 16 and the second corner 18 are shown. Said corners 16, 18 may define the force application points 36 where an external pressing or clamping force is applied on the pre-formed square-shaped lid 70 according to FIG. 9. Due to the cross-sectional view only corners 16, 18 are shown. It is conceivable to apply external pressing or clamping forces at points other than said corners 16, 18, respectively, to provide for a different, however pre-determined pressure distribution between the bottom side 54 and the sealing surface 32 on top of the fluidic device 38.

In the embodiment according to FIG. 9 said preformed square shaped lid 70 has a width which corresponds to the width of said fluidic device 38. The respective length of the preformed square-shaped lid 70 is indicated by reference numeral 24. Said length 24 of said preformed square-shaped lid 70 essentially corresponds to the length of the fluidic device 38. In its non-mounted stage said preformed square-shaped lid 70 has a concave curvature at its topside 52. Reference numeral 76 shows the deepest point of said concave curvature with respect to said first corner 16.

With respect to the bottom side 54 of said preformed square-shaped lid 70 according to FIG. 9 the center of the pre-formed square-shaped lid 70 contacts said sealing surface 32 whereas the edges thereof remain—due to the preformation thereof—without contact to said sealing surface 32, prior to application of external forces at the force application point 36. Once applied, said external forces remove said preformation of the pre-formed square-shaped lid 70 and impose a planar shape thereon.

Similar to the preformed square-shaped lid 70 given in FIG. 7, 8, respectively, upon application of external pressing forces at the respective corners 16, 18, 20 and 22, the latter not shown in the cross-sectional view according to FIG. 9, said preformed square-shaped lid 70 adopts a substantially even flat configuration, which allows for a sealing of the sealing surface 32 of the fluidic device 38 by said bottom side 54 of said square-shaped lid 70 according to FIG. 9. As described above said preformed square-shaped lid 70 may be clamped by a clamping element 46 according to FIG. 4 onto said fluidic device 38 or may be clamped mechanically by bolts or spring biased elements or by a screw/nut-system. Alternatively, said preformed square-shaped lid 70 may be laser welded along the respective edges thereof, i.e. along the length 24 and as well along the width 26. Upon application of a clamping force at the respective four corners 16, 18, 20 and 22, respectively, said preformed square-shaped lid 70 will adopt a substantially even, planar configuration which results in an even pressure distribution over the length of said sealing surface 32, i.e. over the length of said fluidic structure 38, only schematically given here.

FIG. 10 shows the rectangular-shaped lid in full view, covering a fluidic structure in which a preformed rectangular-shaped lid 80 is shown which covers a fluidic structure 38 that has a length 24 which is twice its width 86. Thus, by means of said preformed rectangular-shaped lid 80 a fluidic device 38 having a larger width can be sealed. Said preformed rectangular-shaped lid 80 according to FIG. 10 has four corners 16, 18, 20, 22, respectively, which are suitable for application of an external force as indicated by the arrows 36 given in FIG. 10. Upon application of an external force on said corners 16, 18, 20 and 22, respectively, said preformed rectangular-shaped lid 80 adopts a planar configuration which results in its sealing function of the fluidic device 38. Between said first corner 16 and said second corner 18 a reference line 66 is drawn. With respect to said reference line 66 a third preformation depth 88 corresponds to the preformation i.e. a concave curvature of the topside 52 of said preformed rectangular-shaped lid 80. With respect to the reference line 66 extending between said second corner 18 and said third corner 20 said preformed rectangular-shaped lid 80 adopts a concave configuration 100 which, however, is lesser as compared to the concave configuration along the length 24 of said preformed rectangular-shaped lid 80 according to FIG. 10. Reference numeral 90 depicts a fourth preformation-depth of said width 26 of the preformed rectangular-shaped lid 80 between said second corner 18 and said third corner 20. The bottom side 54 of said preformed rectangular-shaped lid 80 is curved accordingly, however, adopts a convex curvature 104 with respect to said sealing surface 32 of said fluidic structure 38.

FIG. 11 shows a perspective cross-sectional view of a rectangular-shaped lid covering a fluidic structure in which the thickness of the lid is depicted by reference numeral 82. Said preformed rectangular-shaped lid 80 extends over a length which corresponds—after having applied external forces to said pre-formed rectangular lid 80—to the length 24 of said fluidic device 38 which is also shown in FIG. 10. With respect to reference line 66 drawn between said first and said second corner 16, 18, respectively, the preformed rectangular-shaped lid 80 is curved concavely with respect to its topside 52, as indicated by the third preformation depth 88. On the respective ends of said preformed rectangular-shaped lid 80 a part of said concave structure 100 is indicated. Said concave curvature 100 corresponds to an inwardly directed curvature on the topside 52 of said preformed rectangular-shaped lid 80. At its respective bottom side 54 said preformed rectangular-shaped lid 80 has a convex curvature indicated by reference numeral 104. In this cross-sectional view 26′ depicts half of the width of said pre-formed rectangular shaped lid 80. The centre thereof in this illustration does not yet contact said sealing surface 32 as can be derived from a gap 107.

FIG. 12 shows a long-side cross-sectional top view of a preformed-lid according to FIG. 11 in which the center of said bottom side 54 of said rectangular pre-formed lid 80 contacts with a convex and a concave portion said sealing surface 32 of the fluidic device 38. The chord length of said rectangular-shaped lid 80 given in FIG. 12 substantially corresponds to the length 24 of said fluidic device 38. With respect to the reference line 66 drawn between the first corner 16 and the second corner 18 said topside 52 of said rectangular-shape lid 82 has a concave curvature, said bottom side 54 thereof as a result a convex curvature as shown in FIG. 12. Said third preformation depth is indicated by reference numeral 88, the arrow is drawn between the reference line 66 and the topside 52 of the rectangular-shaped lid 80. The thickness of said pre-formed rectangular-shaped lid 80 is indicated by reference numeral 82. The maximum depth according to reference numeral 88 may also be located other than in the center of said concave curvature according to FIG. 12 along the arc between said first corner 16 and said second corner 18. Reference numeral 100 depicts the concave curvature on the edges of said rectangular flat structure according to FIG. 12 extending perpendicular to the plane of FIG. 12. It is conceivable to form said bottom side 54 of said rectangular-shaped lid 80 with a convex curvature with respect to the sealing surface 32 of the fluidic device 38. The reference numerals 100 on the edges of said rectangular-shaped, pre-formed lid 80 show the curvature extending from the cross-section line to the respective first corner 16 and the second corner 18, i.e. one half of said curvature from its deepest to its respective highest point.

In the illustration according to FIG. 13 the embodiment according to FIG. 12 is given from its rearward view. With respect to this different view reference numeral 104 indicates convex curved portions at the bottom side 54 in the edge-area of said rectangular-shaped lid 80. The maximum third preformation depth is indicated by reference numeral 88 between said reference line 66 between said first corner 16 and said second corner 18, respectively to the topside 52 of said rectangular-shaped lid 80. The thickness of the rectangular-shaped lid 80 is indicated by reference numeral 82. For the embodiment shown in greater detail in FIG. 13 the length 24 of said fluidic device 38 corresponds to the chord length of said pre-formed, rectangular-shaped lid 80. Clamping forces or pressure application points may be identical to said first corner 16 and said second corner 18, respectively. In the illustration according to FIG. 13 there is a gap between the center of said bottom side 54 of said rectangular-shaped lid 80 and the center of said sealing surface of the fluidic structure 38 (see FIG. 11, reference numeral 107). For illustration reasons the concave curvature on the topside 52 of said rectangular-shaped lid 80 are not shown in FIG. 13. The concave curvature portions 100 on the topside 52 of said rectangular-shaped lid 80 become clear from the cross-sectional view given in FIG. 12.

In the illustration according to FIG. 14 the contacting points between the bottom side 54 of said rectangular-shaped lid 80 with the edges of said sealing surface 32 are shown. According to this embodiment along the width 26 of said rectangular-shaped lid 80 said pre-formed rectangular-shaped lid 80 is curved convex. With respect to the reference line 66 along the width 26 of said pre-formed rectangular-shaped lid 80 said top side 52 of said rectangular-shaped lid is formed convex, the bottom side 54 of said rectangular-shaped lid 80 does not contact said sealing surface 32 of said fluidic device 38. According to this embodiment it can be derived that the portion of said pre-formed rectangular-shaped lid 80 is curved concave (see reference numeral 74) with respect to the reference line 66 between the first corner 16 and the fourth corner 22, whereas it is pre-formed in a convex manner with respect to the cross-cut portion across the width 26, 24 A depicts the length of one half of said pre-formed rectangular lid 80, 24 B shows one half of the length of said fluidic structure 38. Reference numeral 106 is a convex curvature of said bottom side 52 in the cross-sectional plane, 108 depicts the distance between the centre of said bottom side 54 to the sealing surface 32 in the cross-sectional plane.

The convex curvature is best shown with respect to the reference line 66 along the width 26 at the topside 52 which results in a likewise convex curvature on the bottom side 54 of said pre-formed rectangular-shaped lid 80.

FIG. 15 shows the pre-formed rectangular-shaped lid in a front view of the cross-section area.

According to the illustration in FIG. 15 the convex nature of the curvature of the rectangular-shaped lid 80 becomes clear. Said bottom side 54 thereof does in the center not contact said sealing surface 32 on top of said fluidic device 38. With respect to the reference line 66 the topside 52 of said rectangular-shaped pre-formed lid 80 is curved in a convex manner. However, with respect to the reference line 66 drawn between the first corner 16 and the fourth corner 22 respectively said pre-formed rectangular-shaped lid 80 has a concave curvature as indicated by the fourth preformation depth 90. In this FIG. 108 shows the maximum distance between the bottom side 54 and the sealing surface 32, reference numeral 106 shows the convex curvature of the top side 52 in the cross-sectional plane.

It should be noted that in connection with the afore-mentioned embodiments of the present invention a tight sealing between the embodiments of the lids 30, 50, 70 and 80 and the sealing surface 32 of the fluidic structure 38 are achieved. The connection between said lids 30, 50, 70 and 80, respectively and the fluidic device 38 can be obtained advantageously either by mechanical fastening by means of the fastening element 46 (shown in FIG. 4) or in the alternative by means of laser welding, gluing or the like. Depending on the pressure inside the fluidic device 38 the surface quality of the contact surfaces, i.e. said sealing surface 32 and the bottom side 54 of the lids 30, 50, 70, 80, respectively, and in view of the available external pressure additional sealing layers may be advisable between the contact surfaces. Such additional sealing layers are usually soft, rubber-like material. With regard to mechanical fastening elements 46 it should be noted that those are usually cheap, fast and secure if properly adjusted to fulfill all requirements. The mechanical fastening element 46 can be embodied as screws, clips or frames that hold and press the contact partners, i.e. the embodiments of the lids 30, 50, 70 and 80 and said fluidic device 38 against each other. If an uneven pressure distribution is required the compression forces needed at the respective corners may be varied within a certain extent. Alternatively, said lids 30, 50, 70 and 80, respectively, can be connected to the sealing surface 32 of said fluidic device 38 by means of laser welding. The method of laser welding uses laser irradiation that can be precisely focused to the place with surfaces 32, 54, should be connected to one another, resulting in locally melting the material only inside the connection surfaces. This does not only minimize the amount of energy required but also enables a very exact location of the welding seam, since lasers can have less than 100 μm small focus spots that can be directed very accurately along pre-described paths. By using fast laser scanners or masks even larger areas can easily and quite fast be healed up. It's worthwhile mentioning that heating takes place only at the contact area between said sealing surface 32 and the bottom side 54 of the respective lids 50, 70 and 80 according to the various embodiments, and not in the depth of the material depending on the absorption coefficient that indicates the ability of the material to absorb irradiation of a certain wavelength.

The foregoing relates to preferred exemplary embodiments of the invention, it being understood that other variants and embodiments thereof are possible within the spirit and scope of the invention, the latter being defined by the appended claims. 

1. Method of transforming a pre-determined force or pressure pattern on a lid element through said lid element onto a second element having a planar or non-planar surface comprising the following method steps: a) calculating an optimized preformation-shape of said lid-shaped element and/or said second element depending on the operating parameters of said contacting elements, b) preforming of said lid-shaped element or said second element using a primary shaping or reshaping technique according to the optimized preformation-shape, and c) connecting said lid-shaped element to said second contacting element after application of an external force at at least one predetermined force application point by mechanical fastening or by generating an adhesive bond between said elements.
 2. Method according to claim 1, wherein said preformation according to b) provides for a uniform or intentionally non-uniform pressure distribution over an entire contact surface of said lid-element on said second element.
 3. Method according to claim 1, wherein said lid elements and said second element establish a fluid and/or gas containing or processing device uniformly sealed along a sealing zone, maintaining a uniform sealing pressure.
 4. Method according to claim 1, wherein said lid element and said second element are sealingly connected with one another along a sealing surface of said second element and a bottom side of said lid element.
 5. Method according to claim 1, wherein at least one curvature is preformed in at least one of said elements, in at least one surface thereof.
 6. Method according to claim 5, wherein said at least one curvature is preformed in a convex manner.
 7. Method according to claim 5, wherein said at least one curvature is preformed in a concave manner.
 8. Method according to claim 5, wherein convex and concave curvatures are preformed in said lid element.
 9. Method according to claim 1, wherein said lid comprises four corners, and wherein external forces are applied to said lid element in at least one of said four corners at at least one force application point.
 10. Method according to claim 1, wherein said external forces are applied to said first contacting lid element along the circumference of an upper rim thereof.
 11. Method according to claim 10, wherein said external forces are applied on the upper rim in a plurality of force application points being arranged in predetermined distances with respect to one another.
 12. Method according to claim 1, wherein said lid element is sealingly connected to said second element by mechanical fasteners.
 13. Method according to claim 1, wherein said first lid element is sealingly connected to said second element by laser-welding along the circumference or at distinct points of a contacting area.
 14. Method according to claim 13, wherein after sealingly connecting said lid element to said second element by laser welding or clamping force, a sealing zone is created.
 15. Method according to claim 1, wherein in method step a) said optimized preformation shape is calculated dependent on geometry, material thickness of said lid element, material stiffness, desired pressure tightness and desired pressure distribution and dependent on the pressing forces applied at said at least one force application point.
 16. A fluidic device comprising a sealing surface to which a lid-preformed element is sealingly connected, said lid-preformed element in its mounted stage forming a pressure-tight seal on a second element.
 17. The fluidic device according to claim 16, wherein said lid-preformed element has a circular shape.
 18. The fluidic device according to claim 16, wherein said lid-preformed element has a square- or a rectangular shape.
 19. The fluidic device according to claim 16, wherein said lid-preformed element comprises at least one mechanical fastener.
 20. The fluidic device according to claim 16, wherein said lid-preformed element comprises a mechanical fastener contacting a hinge on corresponding contacting partner.
 21. The fluidic device according to claim 16, wherein said lid-preformed element has a convex curvature on its bottom side towards said sealing surface.
 22. The fluidic device according to claim 21, wherein a uniform pressure distribution is maintained within a sealing area.
 23. The fluidic device according to claim 21, wherein an intentionally non-uniform pressure distribution is maintained within a sealing area.
 24. The fluidic device according to claim 22, wherein the uniform or the intentionally non-uniform pressure distribution between said lid-pre-formed element and said fluidic device is maintained either by at least one mechanical fastener or by a laser weld-connection internally.
 25. The fluidic device according to claim 23, wherein the uniform or the intentionally non-uniform pressure distribution between said lid-pre-formed element and said fluidic device is maintained either by at least one mechanical fastener or by a laser weld-connection internally. 